A Danish Microsatellite With a High Scientific Profile
Langlais, B. (1)
Abstract. The aim of this thesis is to chart and understand the multitude of magnetic fields encountered at the surface of the Earth, in near-Earth space, and in near-Mars space. I first introduce terrestrial magnetic field measurement techniques, and I describe in detail the validation and the processing of the Ørsted magnetic measurements. After introducing geomagnetic reference field models (with their limited resolution, due to the poor geographical data distribution), I show the major improvement that the Ørsted magnetic data has had in describing the Earth's magnetic field. My models are computed with a resolution similar to that of the MAGSAT (1979-1980) models. Comparisons of the new models with previous ones lead to a better understanding of the dynamics of the magnetic field at the core-mantle boundary. It also improves the description and the understanding of the magnetic field of lithospheric origin. I then introduce data from the Mars Global Surveyor satellite. These data allow the first model of the Martian magnetic field to be made. This field is a remanent one, frozen in the upper lithosphere. Correlations between the magnetic field and the avalaible topographic and gravimetric data are used to make inferences about the chronology of the martian lithosphere, and more generally about Mars' evolution. Combined studies of the Earth's and Mars' magnetic fields will undoubtedly provide new constraints on the geodynamo and the now-extinct areodynamo.